Generally, transparent conducting films (also referred to as transparent films) have been used for substrates of electronic displaying elements such as a liquid crystal displaying element, an organic electroluminescent element, a plasma display, an electronic paper, an electronic optical element, a solar cell substrate and so forth. The transparent films commonly comprise transparent plates having a conducting (or conductive) layer provided thereon. The transparent plates can comprise glass, plastic, or other suitable material substrates.
Two basic approaches exist to forming a transparent conducting film. In a first approach for forming a transparent conducting film, a wide bandgap semiconductor material is used for the conducting layer. Such semiconductor material may be, for example, indium tin oxide (“ITO”). The semiconductor material can be deposited uniformly as a thin film by processes such as sputter deposition. A second approach for forming a transparent conducting film involves forming a biphasic system comprising a low loading of an opaque conductor in a transparent, insulating matrix. Commonly, carbon nanotubes are used as an opaque conductor because of their high inherent conductivity and their high aspect ratio, both of which facilitate contact between one tube and another, even along a large distance.
In a conventional bundle of carbon nanotubes (CNTs) provided on a substrate, as tube loading increases, the number of tube-tube contacts increases. At the same time, however, the transparency of the conductive layer and of the film decreases.